I will echo Razvan, based on the research I did, not actually owning one. I decided to buy the Canon EF-S 10-22mm lens, but came VERY close to buying the 11-16mm Tokina, instead. I own a most excellent 100mm Macro made by Tokina, and believe their lenses to be very good.

If you are on a budget, then get the older Sigma 10-20mm f/4-5.6 EX DC HSM. This doesn't take in as much light as the Tokina, but if you are doing landscapes, then you won't need it. Also, it goes wider, and zooms in more, than the Tokina.

Sigma has a newer f/3.5 version of this lens, but it is more expensive.

The only reason I would advise the Tokina is if you need more light intake.

If AF is'nt important to you then I'd recommend a manual focus prime as they are generally sharper than zooms.
I dont think you actually mentioned how wide you want to go but 17mm primes go very cheap. I picked a Tokina 17mm f3.5 RMC up for about $15. The Tamron SP 17mm f3.5 is better but it cost me about $180.
Both are FF lenses.
If you want to go wider than 17mm on the cheap but dont want a fish-eye then the Sigma 14mm f3.5 is probably about as wide as it gets for a cheap manual focus FF rectalinear prime. Got mine for about $100. I really like 14mm on crop format as it gives the equivalent FOV as a 24mm lens on FF.
Here are some Sigma 14mm samples...All wide open and handheld:

If you want to go go wider than that on crop format, without resorting to a fish-eye lens, then you will need a modern AF zoom.
The Sigma AF 8-16mm EX is currently the widest rectaliner zoom on the market for crop format and its an excellent lens...But perhaps a bit over your budget in the price department.
The Sigma 10-20mm f3.5, again for crop format, is also excellent but again perhaps a bit too pricey.
If you want a really wide fish-eye lens for crop format then again, its Sigma that offer the widest available. The Sigma 4.5mm EX is currently the widest fish-eye lens with AF on the market.